6.1 George Armstrong Custer (left center in light clothing) leads a military expedition into the Black Hills of Dakota Territory in 1874. Custer's incursion violated the Fort Laramie Treaty of 1868 and laid the groundwork for war between the Lakota and the United States when he announced that gold had been discovered in this most sacred of the Lakota's lands. Photograph by William H. Illingworth.